1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus using the same.
2. Description of the Related Art
In recent years, in video cameras and digital cameras, small-sizing and slimming of a zoom lens have been progressing. Moreover, with a spread of photography applications, in addition to fulfil the requirement of small-sizing and slimming, widening of an angle of view and high zooming ratio, have been sought.
Zoom lenses fulfilling such requirements have been disclosed in Japanese Patent Application Laid-open Publication Nos. 2011-75985 and 2012-98699. The zoom lenses in Japanese Patent Application Laid-open Publication Nos. 2011-75985 and 2012-98699 are zoom lenses of a type having five or more than five lens units. Here, refractive power of each lens unit in order from an object side is a positive refractive power, a negative refractive power, a positive refractive power, a negative refractive power, and a positive refractive power.
In the zoom lens disclosed in an example 1 of Japanese Patent Application Laid-open Publication No. 2011-75985, a telephoto ratio at a telephoto end (a ratio of an overall length of the lens to a focal length of (at) the telephoto end) is about 0.87, and a zooming ratio is about 34. In the zoom lens disclosed in an example 1 and an example 5 of Japanese Patent Application Laid-open Publication No. 2012-98699, the telephoto ratio is about 1.05 and the zooming ratio is about 41.
Small-sizing and high zooming ratio are demanded in a zoom lens, and further improvements are sought to achieve both demands. Also, with the achievement of high zooming ratio, suppressing an effect of camera-shake is sought. Moreover, improvements for maintaining a favorable optical performance are sought, even when a high zooming ratio is achieved. The favorable optical performance means that occurrence of various aberrations is suppressed sufficiently.